Asymmetric carboaluminations

Allyl aryl ethers undergo accelerated Claisen and [1,3] rearrangements in the presence of a mixture of trialkylalanes and water or aluminoxanes. The addition of stoichiometric quantities of water accelerates both the trimethylaluminum-mediated aromatic Claisen reaction and the chiral zirconocene-catalyzed asymmetric carboalumination of terminal alkenes. These two reactions occur in tandem and, after oxidative quenching of the intermediate trialkylalane, result in the selective formation of two new C-C bonds and one C-0 bond (Eq. 12.70).153 Antibodies have also been developed to catalyze Claisen154 and oxy-Cope155 rearrangements. 

Zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA reaction) 272... 

Scheme 32 Three discrete protocols of the synthesis of Me-branched alcohols via Zr-catalyzed asymmetric carboalumination.

Asymmetric amplification, in diisopropylzinc additions, 2, 386 Asymmetric arylation, phenols with lead triacetates, 9, 399 Asymmetric carboalumination, Zr-catalyzed, alkenes, 10, 272 Asymmetric carbonyl-ene reaction, characteristics, 10, 559 Asymmetric catalysis... 

Figure 8.12 Stereo- and enantioselective synthesis of (S,f ,f ,S,f ,S)-4,6,8,10,16,18-hexa-methyldocosane via iterative zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA reaction).

Wipf et al. reported tandem aromatic Qaisen rearrangement/catalytic asymmetric carboalumination using a chiral zirconocene catalyst [36]. 

Zr>Catalyzed Asymmetric Carboalumination of Alkenes (ZACA) ZACA-Pd- or Cu-Catalyzed Cross-Coupling Sequential Processes as a General Route to Enantiomerically Enriched Chiral Oiganic Compounds... 

Zirconium-Catalyzed Asymmetric Carboalumination of Alkenes (ZACA Reaction)... 

ZACA Zirconium-catalyzed Asymmetric Carboalumination of Alkenes anj CH2R are very similar... 

In the last decade, zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA) has been developed [65]. Most commonly used catalyst is bis... 

The palladium-mediated cross-coupling of organozinc reagents, derived from the asymmetric carboalumination of allyl alcohol, with (iodoethynyl)trimethylsilane (eq 9), has also been reported en route to callystatin... 

The carbometalation reaction has been reviewed recently [28-30]. Negishi has demonstrated that zirconium(TV) complexes catalyze the carboalumination of MesAl to various alkynes and enynes [31]. Also the Zr-catalyzed asymmetric carboalumination of aUcenes (ZACA reaction) [32-34] has found important applications in the synthesis of natural products [35-37]. Especially efficient was the asymmetric synthesis of insect pheromones such as (S. / ./ ,S. / ,S)-4,6,8,10,16,18-hexamethyl-docosane (88) (Scheme 8) [38]. 

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